The present invention is directed to a spray machine which comprises a driven rotor unit which rotor unit carries at its periphery a multitude of bushings which are open at both sides and which are arranged with their axes pointing in a direction with at least one direction component parallel to an axis of said rotor and comprising, stationary with respect to a machine frame, a filling opening at a filling arrangement, a pressurized air inlet opening, an ejection opening being located opposite to said pressurized air inlet opening considered in direction of said axes of said bushings, whereby all said openings are so arranged that when said rotor unit rotates, the openings of said bushings pass over said openings, and further comprising, stationary with respect to said machine frame, at both sides of said rotor unit, sealing plate arrangements.
Such spray machines are known.
In the area of the filling opening where the spray medium is filled into the bushings of the rotor, in the area of the pressurized air inlet where ejecting pressurized air acts from one side onto the spray medium filled bushings and in the area of the ejection opening, where pressurized air driven spray medium is ejected out of the bushing into a respective conveying line, sealing is necessary between the machine rotor unit and the machine stator. This is also true in the area of the filling opening if one wants to prevent contamination of the surrounding of the machine when ejecting dusty medium. It is customary to realize such sealings by means of stationary sealing plate arrangements.
It is further customary to bias the upper and the lower sealing plate arrangements with a surface pressure and substantially uniformly towards the end faces of the rotor unit. This to ensure the required seal. Such requirements are governed by the increased sealing necessity in the area of the pressurized air inlet and in the area of the ejection opening. Thereby, considerable friction forces act on the rotor unit and the respective torque has to be generated by a driving motor driving the rotor unit. Therefore powerful and bulky drive motors are required to drive the rotor unit of the spray machine.
In FIG. 1 there is schematically shown a concrete spray machine which works according to the rotor principle. Concrete is filled into a hopper 1. Below the hopper 1 a rotor 8 rotates, driven around an axis A. The rotor comprises, similar to a revolver, a multitude of receptacle bushings 7 to receive concrete. At the bottom of hopper 1 there is provided a stationary filling opening 6 so that sequentially the bushings 7, brought into alignment with the opening 6 as the rotor rotates, are filled. The bushings 7, which are respectively brought into alignment with the filling opening 6, are closed at their bottom by means of a stationary sealing plate 9.
On the side of the hopper 1 there is further provided a conduit 4 for pressurized air which is brought via an opening 5 for pressurized air into operational connection with a respective bushing 7 rotated into alignment with said opening 5. In this ejection position, aligned with the opening 5 for pressurized air, the respective bushing 7 is also aligned with an ejection opening 3 at its bottom, which opening 3 is provided in the sealing plate 9. The sealing plate 9 closes, on one hand in filling position, the respective bushing 7 at its bottom and establishes, on the other hand, for ejecting the concrete filled in the respective bushing 7, tightness around the ejection opening 3. An upper sealing plate 10 acts on the upper side of the rotor 8.
The ejection opening 3 propagates via a bent section 11 into a conveying conduit which is not shown in the figure. A conveying pipe 13 for pressurized conveyor air abuts into the curved section 11. A driven stirring arrangement 15 acts within hopper 1.
Such a concrete spray machine works according to the so-called "low density jet principle" at which the medium to be ejected, concrete, practically floats within the pressurized air which is fed by conduit 13. Thereby, the concrete is conveyed along the conveying conduit connected to the bent section 11. Along this conveying conduit water and possibly further additives are controllably added to the spray medium.